10.5. Event Handler Syntax

The names
of events (and their corresponding
event handlers) are predetermined by ActionScript. Button event
handlers are defined using on
(eventName), and movie clip
event handlers are defined using onClipEvent
(eventName), where
eventName is the name of the event to be
handled.

Hence, all button event handlers (except
keyPress, which also
requires a key parameter) take the form:

on (eventName) {
statements
}

A single button handler can respond to multiple events, separated by
commas. For example:

on (rollover, rollOut) {
// Invoke a custom function in response to both the rollOver and rollOut events
playRandomSound( );
}

All movie clip event handlers take the form:

onClipEvent (eventName) {
statements
}

Unlike button handlers, clip handlers can respond only to a single
event.